How to choose the correct injection mold gate location?
3. Gate size
The size of the gate can be determined by the cross-sectional area and the length of the gate. The optimal size of the gate can be determined by the following factors:
1) flow characteristics of rubber
2) thickness of modules
3) amount of rubber material injected into mold cavity
4) melting temperature
5) mold temperature
4. Gate balance
If a balanced runner system cannot be obtained, the following gate balancing method can be used to achieve the goal of uniform injection molding. This method is suitable for working dies with a large number of cavities. There are two ways to balance the gate: changing the length of the gate and changing the cross section area of the gate. In the other case, where the cavity has different projected areas, the gate also needs to be balanced. At this point, to determine the size of the gate, the size of one of the gates should be determined, and the ratio between the size of the gate and the corresponding hole volume should be calculated. Then, the ratio should be applied to the comparison between the gate and the corresponding hole, and the size of each gate can be calculated successively. After the actual trial injection, the balance operation of the gate can be completed.
5.Direct or large gate
The runner supplies plastic directly to the finished product and the runner is attached to the finished product. In the two plate die, the large nozzle is usually a, but in the three plate die or hot runner die design, can be more than one beer. Disadvantages: the appearance of the finished product will be affected by the formation of a nozzle on the surface of the finished product.
6.Release Angle of nozzle, length of nozzle
As a result, the size of the nozzle can be reduced by reducing the size of the nozzle. However, the diameter of the nozzle is affected by the diameter of the nozzle, and the nozzle to be easy to mold, the release Angle should not be less than 3 degrees, so only the nozzle length can be reduced, with a longer nozzle.
Gate selection:The gate is the connection part between the runner and the mold cavity, and also the last part of the feeding system of the injection mold. Its basic functions are:
1)make the molten plastic from the flow channel enter the full mold cavity at the fastest speed.
2) after the mold cavity is filled, the gate can be quickly cooled and closed to prevent the reflux of plastic that has not been cooled in the mold cavity.PS :(the nozzle occupies A very important part in the mold. The product is formed after heating the dissolved plastic and injecting it into the mold through the nozzle. It is assembled in the middle of the front mold (panel A).
7. To summarize
The design of gate is related to the size and shape of plastic parts, mould structure, injection process conditions and properties of plastic parts. But on the basic role, the gate section should be small, short length, because only in this way can meet the requirements of increasing the flow material speed, rapid cooling and sealing, easy to separate plastic parts and the minimum gate residue. The key points of gate design can be summarized as follows:
1) the gate is set at the part of the thick section of the plastic part, so that the molten material flows from the thick section to the thin section to ensure the complete filling of the mold;
2) the choice of gate location should be conducive to eliminating air in the mold cavity;
3) it is not suitable for the sprue to cause the molten material to rush directly into the mold cavity, otherwise the vortex will be generated and leave the swirl marks on the plastic parts, especially the narrow sprue is more prone to such defects;
4) the choice of sprue location should prevent the occurrence of stitching lines on the plastic surface. Especially in circular or cylindrical plastic parts, a cold material well should be added at the melting material pouring joint of the sprue surface;
5) the gate position of the injection mold with slender core should be far away from the molding core, so that the molding core will not be deformed by material flow;
6) when forming large or flat plastic parts, double gate can be used to prevent warping, deformation and material shortage;
7) the gate shall be set as far as possible in a position that does not affect the appearance of the plastic parts, such as the bottom of the edge;
8) the size of the gate depends on the size and shape of the plastic parts and the properties of the plastic;
9) when designing multiple cavity injection molds, consider the balance of sprue in combination with the balance of runner, and try to make the molten material evenly filled at the same time.